Composition and method of improving the green strength of unvulcanized elastomers

ABSTRACT

The green strength of elastomers is improved by the addition of semi-crystalline butene polymers selected from the class consisting of polybutene and interpolymers made from 1-butene monomer and at least one monomer selected from the class consisting of alpha-olefins, non-conjugated dienes, and non-conjugated polyenes. The semi-crystalline butene polymer is mixed with a desired elastomer such as natural or synthetic cis-1,4-polyisopropene, or a synthetic elastomer made from monomers selected from the class consisting of conjugated dienes having from 4 to 10 carbon atoms, interpolymers of said dienes among themselves or with vinyl substituted aromatic hydrocarbon compounds having from 8 to 12 carbon atoms, or polyalkenylenes. The mixing or blending of the butene polymer and the elastomer may be through conventional methods such as cement mixing or mastication.

BACKGROUND OF THE INVENTION

The present invention relates to improved green strength of unvulcanizedelastomers. More specifically, the present invention relates to theimprovement of green strength by adding semi-crystalline butene polymersto elastomers. Science and technology in the elastomer field haveimproved to such an extent that synthetic elastomers have supplementedor replaced natural rubber to a great extent in the fabrication of tiresand other rubber products. Stereo-regular polymers and particularlysynthetic high cis-1,4-polyisoprene have demonstrated physicalproperties similar to natural rubber and thus are capable of becoming acomplete replacement for it. A major deficiency of many syntheticelastomers including cis-1,4-polyisoprene is their lack of sufficientgreen strength required for satisfactory fabrication of tires andindustrial goods. The abatement of this deficiency has long been soughtby the art and would greatly facilitate in the replacement of naturalrubber which is solely produced in tropical climates.

The term "green strength" while being commonly empolyed and generallyunderstood by persons skilled in the rubber industry, is nevertheless adifficult property to precisely define. Basically, it is that propertyof a polymer, common in natural rubber, which contributes the properbuilding characteristics where multiple components are empolyed andwhich result in little or no relative movement of the assembledcomponents subsequent to assembly and prior to initiation of the curingopeation. "Tack" is also an important property but the lack of track isusually readily overcome by the addition of well known and conventionaltackifying agents. Thus, green strength, that is adequate mechanicalstrength for fabricating operations necessarily carried out prior tovulcanization with synthetic homopolymers or interpolymers, is lacking.That is, generally the maximum or "yield" stress which the unvulcanizedcompositions will exhibit during deformation is rather low and moreover,the stress drops off quite rapidly as the deformation continues. Thus,unvulcanized strips or other forms of the elastomer often pull apart ina taffy-like manner during building operations. Although numerousadditives and compounds have been utilized in association with variouselastomers and particularly synthetic cis-1,4-polyisoprene, adequateimprovement in green strength has generally not been accomplished.

Green strength has generally been measured by stress/strain curves ofunvulcanized compounds. Usually, the performance of a green compound isbased upon two points of the stress/strain curve, namely the first peakor yield point and the ultimate or breaking tensile. Improvement ineither of these stress properties indicates improved green strength.

Among the various additive compounds or agents which have been utilizedto improve green strength of synthetic elastomers are numerous nitrosocompounds as set forth in U.S. Pat. Nos. 2,457,331; 2,447,015;2,518,576; 2,526,504; 2,540,596; 2,690,780; and 3,093,614. Additionally,various dioxime compounds have been utilized such as those set forth inU.S. Pat. Nos. 2,969,341; 3,037,954; 3,160,595; and British Pat. No.896,309. Yet another class of additives or compounds is the diesters of5-norbornene as set forth in U.S. Pat. Nos. 3,817,883 and 3,843,613.

A Romanian article was published in Materiale Plastice No. 10 (11),604-607 (1973) entitled "INFLUENCE OF ADDITIONS OF POLYBUTYLENE WITHDIFFERENT MOLECULAR WEIGHT ON THE PROPERTIES OF COMPOSITIONS OFCIS-POLYISOPRENE SYNTHETIC RUBBER" and prepared by B. Mehr and T.Volintiru. This article discloses the use of polybutylene which is mixedwith synthetic or natural rubber to give increases in variousproperties. As set forth on Page 2 of the translation of the article,the molecular weight must be low and cannot exceed 10,000 sinceotherwise a mixture with a synthetic rubber cannot be obtained. Thearticle does set forth data which shows that various physical propertiesare improved such as the increase in resistance to repeated bending andincreased ozone resistance. However, as plainly evident by the table setforth on Page 3 of the translation, no appreciable increase in tensileor rupture strength is obtained when polybutylene is utilized. In fact,the bottom of Page 3 of the translation clearly states that incomparison with low pressure polyethylene utilized as a mixture, thepolybutylenes do not improve the green strength of cis-polyisoprenesynthetic rubber. Thus, this article is not pertinent.

Another U.S. Patent, namely U.S. Pat. No. 3,909,463 assigned to AlliedChemical Corporation, relates to the preparation of graft copolymerswherein a synthetic rubber is grafted onto an olefin polymer backbonesuch as polypropylene and polybutylene whereby composition is formedwhich is free of substantial amounts of cross-linked rubber. The amountof olefin polymer utilized is from 40 percent to about 99 percent byweight. Additionally, a bifunctional phenol-aldehyde condensate isutilized in forming the graft copolymer. The grafted copolymer formedappears to be a high impact resin.

The present application is readily distinquished from the abovereference in that a physical blend is formed as opposed to a chemicalreaction for forming a graft copolymer, a rubber compound is formed asopposed to a high impact resin, low amounts of polybutylene are utilizedin comparison to the high amount contained in the graft copolymer and nobifunctional phenol-aldehyde condensate is utilized whatsoever in thepresent invention.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide elastomershaving improved green strength.

It is another object of the present invention to provide improved greenstrength elastomers, as above, which contain a semi-crystalline butenepolymer.

It is still another object of the present invention to provide improvedgreen strength elastomers, as above, where the elastomers are natural orsynthetic cis-1,4-polyisoprene, or synthetic elastomers made frommonomers selected from the class consisting of conjugated dienes havingfrom 4 to 10 carbon atoms, or interpolymers of said conjugated dienesamong themselves or with monomers selected from the group consisting ofvinyl substituted aromatic hydrocarbon compounds having from 8 to 12carbon atoms, or polyalkenylenes.

It is a further object of the present invention to provide improvedgreen strength elastomers, as above, where the elastomers are commonrubbers such as natural or synthetic cis-1,4-polyisoprene,cis-1,4-polybutadiene, solution or emulsion SBR (styrene/butadienerubber), poly(2,3-dimethylbutadiene), polypiperylene, 3,4-polyisoprene,1,2-polybutadiene, interpolymers of dienes such as copolymers ofisoprene and butadiene, copolymers of 2,3-dimethylbutadiene andpiperylene, and polymers obtained by the ring opening of cycloolefins.

It is still another object of the present invention to provide improvedgreen strength elastomers, as above, wherein the elastomers includereclaimed rubber.

It is still a further object of the present invention to provideimproved green strength elastomers, as above, wherein the butene polymeris a reasonably high molecular weight polymer selected from the classconsisting of a homopolymer of 1-butene, and interpolymers made from1-butene monomer with at least one monomer selected from the classconsisting of alpha-olefins having from 2 to 16 carbon atoms,non-conjugated dienes of the general formula: ##STR1## where R₁, R₂ andR₃ is a hydrogen, a lower alkyl group containing up to four carbonatoms, or an aryl group, R₄ is an aryl group or a lower alkyl groupcontaining up to nine carbon atoms and n is an integer having values offrom 1 through 6, and wherein the said R₁ 's in the ##STR2## may besimilar or dissimilar, and non-conjugated alpha, omega-polyenes havingfrom 6 to 36 carbon atoms which may or may not contain internalunsaturation, wherein butene in the interpolymers comprises from 99.9 to65 mole percent of the total monomers charged.

These and other objects of the present invention will become apparentfrom the following specification which describes in detail theembodiments without attempting to discuss all of the modifications inwhich the invention might be embodied.

In general, a process for producing elastomer blends having improvedgreen strength comprises a butene polymer with an elastomer, said butenepolymer is defined as a reasonably high molecular weight polymerselected from the class consisting of polybutene and interpolymers madefrom 1-butene monomer and at least one monomer selected from the classconsisting of alpha-olefins having 2 through 16 carbon atoms,non-conjugated dienes having the general formula: ##STR3## where R₁, R₂,and R₃ is a hydrogen, a lower alkyl group containing from one to fourcarbon atoms, or an aryl group; where R₄ is an aryl group or a loweralkyl group containing from one to nine carbon atoms, and n is aninteger having a value of from 1 to 6, and wherein the said R₁ 's in the##STR4## group may be similar or dissimilar; and non-conjugated alpha,omega-polyenes having from 6 to 36 carbon atoms which may or may notcontain internal unsaturation, wherein butene in said interpolymerscomprises from 99.9 to 65 mole percent of the total monomers; saidelastomer selected from the group consisting of naturalcis-1,4-polyisoprene, synthetic cis-1,4-polyisoprene, and syntheticelastomers; said synthetic elastomers made from monomers selected fromthe group consisting of conjugated dienes having from 4 to 10 carbonatoms, interpolymers of said conjugated dienes among themselves or withmonomers of vinyl substituted aromatic hydrocarbons having from 8 to 12carbon atoms, and polyalkenylenes.

In general, an elastomer composition having improved green strengthcomprises a semi-crystalline butene polymer of reasonably high molecularweight existing in a blend with an elastomer wherein said butene polymerand said elastomer are set forth herein immediately above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the concepts of the present invention, improved greenstrength of elastomers is obtained through the addition ofsemi-crystalline butene polymers. The method of addition of the butenecopolymers to the elastomers may be any conventional method such asblending the polymer with the desired synthetic rubber(s) in a cementphase followed by solvent removal or by the addition of the desiredamount of polymer to the synthetic rubber during compounding. Of course,any other blending or mixing method may be utilized since the onlyrequirement is that the butene polymer of the present invention bedispersed within the elastomer.

The mechanism of green strength improvement of the elastomers withbutene polymers is not established. Presumably, the butene polymersimprove the green strength by providing sites of crystallinity in theblend. In general, the crystalline polymers for imparting green strengthimprovement possess a certain desirable melting temperature. If themelting temperature is too high, it will not blend easily with theelastomer composition. A desirable melting temperature of the butenepolymers of the present invention is generally from about 55° C. toabout 125° C. with a preferred range being from about 70° C. to about100° C. For this reason, the homopolymer of propylene is not suitable.

The crystalline butene polymers are obtained by polymerizing 1-butenealone to form polybutene or by forming interpolymers from 1-butenemonomer and at least one monomer selected from the class consisting ofalpha-olefins having 2 through 16 carbon atoms, non-conjugated dieneshaving the general formula: ##STR5## where R₁, R₂, and R₃ is a hydrogen,a lower alkyl group containing from one to four carbon atoms, or an arylgroup; where R₄ is an aryl group or a lower alkyl group containing from1 to 9 carbon atoms, and n is an integer having a value of from 1 to 6,and wherein the said R₁ 's is in the ##STR6## group may be similar ordissimilar; and non-conjugated alpha, omega-polyenes having from 6 to 36carbon atoms which may or may not contain internal unsaturation. Thebutene interpolymers contain from 99.9 to 65 mole percent, andpreferably from 95 to 70 percent of butene.

Examples of suitable alpha-olefins which can be utilized forcopolymerization with 1-butene include ethylene, propylene, 1-pentene,1-hexene, 1-heptene, 4-methyl-1-pentene, 4-methyl-1-hexene,5-methyl-1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene,1-hexadecene. The linear monoolefins are preferred, with ethylene,propylene, 1-hexene and 1-octene being highly preferred.

Specific examples of suitable dienes of the general formula: ##STR7##include cis-1,4-hexadiene, trans-1,4-hexadiene, cis-1,4-heptadiene,trans-1,4-heptadiene, 4-methyl-1,4-hexadiene, 4-ethyl-1,4-hexadiene,4-butyl-1,4-hexadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,4-heptadiene,4-methyl-1,4-nonadiene, 3,4-dimethyl-1,4-hexadiene, cis-1,4-nonadiene,trans-1,4-nonadiene, 6-phenyl-1,4-hexadiene, 5-phenyl-1,4-hexadiene,5-p-tolyl-1,4-hexadiene, 4,5-diphenyl-1,4-hexadiene, cis-1,4-octadiene,trans-1,4-octadiene, trans-1,4-decadiene, trans-1,4-dodecadiene,cis-1,4-dodecadiene, trans-1,4-tetradecadiene, cis-1,4-tetradecadiene,1,5-heptadiene, 1,6-octadiene, and 7-methyl-1,6-octadiene.

Preferred dienes include trans-1,4-hexadiene, trans-1,4-heptadiene, and5-methyl-1,4-hexadiene.

Specific examples of suitable alpha, omega-polyenes which may beutilized to form butene interpolymers include 1,6-heptadiene,1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,10-undecadiene,1,11-dodecadiene, 1,12-tridecadiene, 1,13-tetradecadiene,1,4,9-decatriene, 1,5,9-decatriene, 1,6,9-decatriene,1,5,9,13,17-octadecapentadiene, 1,9,17-octadecatriene, 1,4,7-octatriene,and the like. Preferred alpha, omega-polyenes are 1,7-octadiene,1,9-decadiene and 1,5,9-decatriene.

As employed in this specification, inherent viscosity is defined as thenatural logarithm of the relative viscosity at 30° C. divided by thepolymer concentration for a 0.05 to 0.25 percent (W./V.) solution intoluene, chloroform, tetrachlorethylene or other suitable solvent andexpressed in units of deciliters per gram (dl./g.). The butene polymersof the present invention have an inherent viscosity of from about 0.5 toabout 10.0 dl./g. and preferably from about 1.0 to about 4.0 dl./g.

Coordination catalysts prepared from organometallic-transition metalcompounds may be utilized in the present invention in the preparation ofthe butene polymers. These catalysts are well known to the art and donot constitute a part of this invention. Examples of such catalystsystems include triethylaluminum-vanadium tetrachloride,triethylaluminum-α-titanium trichloride, diethylaluminumchloride-α-titanium trichloride, and triethylaluminum-titaniumtetrachloride. Of course, many other catalysts may be utilized.

Generally, the butene polymer is blended with various known elastomers.The various elastomers include natural or syntheticcis-1,4-polyisoprene, or synthetic elastomers made from monomersselected from the group consisting of conjugated dienes having from 4 to10 carbon atoms, or interpolymers of said dienes among themselves orwith monomers selected from the group consisting of vinyl substitutedaromatic hydrocabon compounds having from 8 to 12 carbon atoms, or withpolyalkenylenes. Specific examples of suitable elastomers includenatural cis-1,4-polyisoprene rubber such as guayule and hevea, syntheticcis-1,4-polyisoprene, cis-1,4-polybutadiene, solution or emulsionstyrene/butadiene rubber, polypiperylene,poly(2,3-dimethylbutadiene),3,4-polyisoprene, 1,2-polybutadiene, and thelike. The terms cis-1,4-polyisoprene and cis-1,4-polybutadiene implythat these rubbers contain about 70 percent or more of thecis-1,4-structure. The term 3,4-polyisoprene, as used here, impliesabout 30 percent or more of the 3,4-structure. Likewise,1,2-polybutadiene denotes about 30 percent or more of the 1,2-structure.Examples of specific interpolymers made from the conjugated dienesinclude interpolymers of isoprene and butadiene, isoprene andpiperylene, 2,3-dimethylbutadiene and piperylene, and the like. Theelastomeric interpolymers of the conjugated dienes with the vinylsubstituted aromatic compounds will contain from about 2 percent toabout 50 percent by weight of the vinyl compound with a desired rangebeing from 5 percent to about 35 percent. A preferred range is fromabout 15 percent to about 20 percent. Examples of suitablevinyl-substituted aromatic compounds include styrene,alpha-methylstyrene, ortho-, para-, and meta-methyl and ethyl styrenes,and the like. Styrene and alpha-methylstyrene are preferred. Hence,examples of such interpolymers will include those prepared from sytreneand butadiene, styrene and isoprene, alpha-methylstyrene and butadiene,and the like.

Polyalkenylenes, according to the present invention, mean homopolymersof cyclomonoolefins, homopolymers of non-conjugated cyclopolyolefins,and interpolymers of cyclomonoolefins with non-conjugatedcyclopolyolefins. Typical examples of polyalkenylenes arepolypentenylene which is a homopolymer of cyclopentene having from about5 to 99 percent cis and 95 to 1 percent trans configurations of doublebonds; polyoctenylene which is a homopolymer of cyclooctene having about25 to 95 percent cis and 75 to 5 percent trans configurations of doublebonds, polyoctadieneylene which is a homopolymer of 1,5-cyclooctadienehaving about 25 to 85 percent cis and 75 to 15 percent transconfigurations of double bonds; copolymers of cyclopentene anddicyclopentadiene containing 10 to 40 mole percent dicyclopentadiene;and copolymers of cyclooctene and 1,5-cyclooctadiene containing 10 to 50mole percent cyclooctadiene.

Generally the preferred elastomers for practicing the present inventioninclude natural or synthetic cis-1,4-polyisoprene,cis-1,4-polybutadiene, 1,2-polybutadiene, and the copolymer of styreneand butadiene.

Generally, an amount of synthetic (or natural) rubber is utilized sothat the range of the butene polymers is from about 2 to about 25 partsby weight per 100 parts of elastomer. A preferred range is from about 3to about 12 parts per 100 of elastomer. The number average molecularweight of the synthetic rubber may desirably range from about 100,000 toabout 500,000 with a more desirable range being from about 150,000 toabout 300,000. The number average molecular weight of the butenepolymers may desirably range from about 30,000 to about 500,000, with amore desirable range being from about 50,000 to about 300,000.

The butene polymers of the present invention which are added to thenatural or synthetic rubbers can also be utilized to improve the greenstrength of reclaimed rubber. Reclaimed rubber may be defined as theproduct resulting from the treatment of ground scrap rubber by theapplication of mechanical operations, heat and chemical agents, wherebya substantial regeneration of the rubber compound to its originalplastic state is effected, thus permitting the product to be processed,compounded, and vulcanized. The composition of the reclaimed rubber, ofcourse, will vary according to the source or items reclaimed and thuscan vary from batch to batch and also due to the reclaiming techniqueutilized. Generally, along with the reclaimed rubber and the butenepolymers, an amount of at least 5 percent by weight of synthetic ornatural rubber is also added. The amount of butene polymers to the totalweight of the blend is the same as before, that is, from 2 to 25 weightpercent.

Regardless of whether synthetic rubbers and/or reclaimed rubber isutilized, the butene polymers may be dispersed into the elastomeraccording to conventional methods. One such method relates to blending asuitable butene polymer of the present invention with the desiredelastomer in a cement phase followed by solvent removal. The cement mixmay be obtained either by mixing together separately prepared componentsor by dissolving components together in the presence of a suitablesolvent. Of course, the solutions of blend components may also beobtained by solution polymerization. The second method, according tocurrent practice, involves the addition of the desired amount of butenepolymer to the elastomer, thus forming the blend during mastication asin an internal mixer or an open mill. Preferably, the butene polymermust at some point be melted and mixed with the elastomer so thatcrystallizable sites will be dispersed throughout the blend and therebyenhance the improvement in green strength.

Either of the two commonly employed methods, or any other method, mayutilize more than one type of elastomer to form the blend. Of course,the blend may also include natural rubber, as noted. Similarly, morethan one butene polymer may be utilized, with the total amount ofpolymer falling within the above-noted ranges.

As previously noted, the blending of the butene polymers results ingreen strength improvement which is usually retained throughout extendedprocessing, including gum stock as well as filled stocks. The additionof the butene polymers in the amounts set forth above does not adverselyeffect the gel content, Mooney, or other raw physical properties.Physical properties of the vulcanized blends are at least equivalent tothose of the elastomers utilized in the blend. Additionally, the blendsshow significantly higher green strength even after extensive milling.This latter behavior is particularly desirable for rubber stocks usedfor the fabrication of complicated articles such as tires and the like.Of course, the blends of the present invention may be used for anyheretofore employed purpose such as for tires in either the body ortread portion, belts, hoses, and other industrial uses. A preferred useis for the manufacture of radial tires, especially truck tires.

Typical or usual compounding ingredients may be added to the blends asduring mastication or other steps. Thus, carbon black, zinc oxide,silica, various clays, oils, waxes, or fibers may be utilized along witha host of other compounds such as antioxidants, antiozonants, curingagents, accelerators, processing agents, and the like, as well known andunderstood by those skilled in the art. Conventional equipment can beutilized for blending the butene polymer with the elastomer as well asfor the compounding material. Thus, the butene polymer can be dryblended with the elastomer by mixing in a conventional rubber mill orinternal mixer, such as a Banbury mixer, either before or during theaddition of the desired compounding materials.

The invention will be more fully understood by the following examples:

PREPARATION OF BUTENE POLYMER

The following examples describe the preparation of a copolymer of1-butene and 1-hexene; 1-hexene (minimum purity of 96 percent) andn-heptane were dried separately by passing through an 18-inch silica gelcolumn. 1-butene (minimum purity of 99 percent) was used directly from acylinder and bubbled into a known quantity of n-heptane is a 2-neckedflask equipped with a dry-ice condenser. The amount of butene dissolvedwas determined from increase in the weight of the flask. To thissolution, an appropriate amount of dried hexene was added to that themolar ratio of butene to hexene was 85:15. The total monomerconcentration was adjusted to about 25 weight percent by the addition ofmore heptane. The entire mixture was carefully sparged with high puritynitrogen.

The polymerization catalyst, α-TiCl₃ /Et₂ AlCl, was prepared in situunder nitrogen by the addition of a 1.5 molar Et₂ AlCl solution inheptane followed by 1.16 molar α-TiCl₃ (contains 0.33 molar AlCl₃)suspension in heptane. The molar ratio of Et₂ AlCl to TiCl₃ was about1.5.

For instance, a solution of 448 grams of 1-butene and 120 grams ofhexene in 2,000 ml. heptane was polymerized under nitrogen at 25° C.with a catalyst prepared from 6 ml. of 1.16 molar α-TiCl₃ suspension inheptane and 7.2 ml. of 1.5 molar Et₂ AlCl solution in heptane. After 120hours, the polymerized mass was precipitated in excess methanolcontaining a phenolic antioxidant. The dried copolymer was obtained in91 percent conversion. Its inherent viscosity was 4.1.

In a similar manner, a solution of 56 grams of butene in 250 ml. ofheptane was polymerized with a catalyst prepared from 1.0 ml. of 1.16molar suspension of α-TiCl₃ and 1.20 ml. of 1.5 molar Et₂ AlCl solutionin heptane. The polymerization was allowed to procede at roomtemperature for 72 hours, the contents being shaken. A suspension ofpolybutene was obtained. After precipitation in excess methanol, acrystalline, white powdery material was obtained in 72 percentconversion by drying in a vacuum oven. It gave endothermic peaks at 98°and 121° C. by differential thermal analysis using a calorimetricattachment.

BLENDING AND COMPOUNDING

Carbon black-loaded synthetic rubber stocks were prepared in an internalmixer in accordance with the following recipe:

    ______________________________________                                        MATERIAL          PARTS BY WEIGHT                                             ______________________________________                                        Elastomer         100                                                         Butene copolymer  0 or 3 to 25                                                HAF black         25                                                          zinc oxide        3                                                           stearic acid      2                                                           ______________________________________                                    

The black-loaded rubber stocks were milled from between 5 and 30 minuteson a 9 inch open mill, 0.050 inch opening, at 140° to 160° F. in 300gram batches. For tests involving vulcanizate properties, sulfur andaccelerator were added in a second Banbury batch.

Green strength tests were conducted in the following manner. Blendcomposition either prepared by cement blending or mastication werepressed under 25 tons of pressure in a 121/2 inch hydraulic press at200° F. for 15 minutes into a 0.10 inch thick strip mold. The stripswere allowed to cool under the same pressure and held at roomtemperature for 16 hours. Then the strips were cut into dumbbells havinga narrowed cross-section of 0.125 by 0.10 inches. The dumbbells werethen pulled at 25° C. on an Instron Tensile Tester at a jaw separationspeed of 10 inches per minute. The stress in pounds per square inch wascalculated at the yield point (initial tensile peak) and at break. Theelongation at break was expressed as percent increase in the originallength of the dumbbell between bench marks on the narrowedcross-section.

Data for yield stress, stress-at-break and percent elongation-at-breakfor carbon black-loaded blends of Natsyn 200 (syntheticcis-1,4-polyisoprene, greater than 95 percent cis content, a trademarkof The Goodyear Tire and Rubber Company) are shown in Tables I, II, IIIand IV. Table V shows the data for the same properties for a 35/35/30blend of natural rubber/Butene (cis-1,4-polybutadiene, trademark of TheGoodyear Tire and Rubber Company)/SBR (84 percent butadiene, 16 percentsytrene, extended with 37.5 phr oil). The blends of the materials setforth in Tables I through V were made in a Size B Banbury according to amethod set forth above.

                                      TABLE I                                     __________________________________________________________________________    Green Strength Comparisons for Black-Loaded Banbury Stocks of                 Several Rubbers. Blends Shown are with 5 PHR of                               a 90/10 1-Butene/1-Hexene Copolymer*                                                      Control Stocks                                                                              Blends                                                      Milling                                                                           Yield                                                                             Break     Yield                                                                             Break                                           Diene Rubber                                                                          Time                                                                              Stress                                                                            Stress    Stress                                                                            Stress                                          Type    (min)                                                                             (psi)                                                                             (psi)                                                                             (% Elong)                                                                           (psi)                                                                             (psi)                                                                             (% Elong)                                   __________________________________________________________________________    Natsyn 200.sup.1                                                                      0   41  97  (1500)                                                                              100 220 (400)                                               5   27  13  (2200)                                                                              34  34  (2000)                                              10  27  12  (2500)                                                                              30  20  (1800)                                              30  24   5  (2500)                                                                              25  11  (2000)                                      Emulsion SBR.sup.2                                                                    0   50  25  (500) 69  69  (300)                                               5   33  22  (750) 46  50  (300)                                               10  32  18  (600) 43  34  (400)                                               30  31  17  (500) 41  32  (300)                                       1,2-PBd.sup.3                                                                         0   30  22  (500) 66  66  (150)                                               5   32  21  (300) 36  25  (300)                                               10  31  21  (300) 38  28  (350)                                               30  30  16  (400) 37  25  (300)                                       Natural Rubber                                                                        0   51  285 (1,000)                                                                             310 755 (580)                                               5   33  73  (1,000)                                                                             85  217 (570)                                               10  31  70  (1,200)                                                                             41  108 (880)                                               30  24  29  (900) 32  75  (940)                                       __________________________________________________________________________     *Molar charge ratio; polymerization temperature: 30° C.; inherent      viscosity, 4.9.                                                               .sup.1 Synthetic cis1,4-polyisoprene (>96% cis content), commercially         available from The Goodyear Tire and Rubber Company.                          .sup.2 Styrene/butadiene rubber, 84% butadiene and 16% styrene, with 37.5     parts oil.                                                                    .sup.3 Medium vinyl polybutadiene commercially available from ISR, 48%,       1,2structure, Contained 37.5 parts oil.                                  

As is readily apparent from Table I, the green strength for the threesynthetic elastomers as well as natural rubber was greatly increased byblending with 5 phr of a 90/10 butene/hexene copolymer. Thus, the yieldstress of the blend of synthetic cis-1,4-polyisoprene (Natsyn 200) andbutene/hexene copolymer was significantly higher than that of the Natsyncontrol, even after milling for 10 minutes. Likewise, thestress-at-break was higher for the blend than for the control.

Similarly, the blends, whether milled or not, of emulsion SBR, 1,2-PBd,and natural rubber with the butene/hexene copolymer, show higher yieldstress and stress-at-break values than the corresponding rubbers withoutthe addition of the butene/hexene copolymer.

                                      TABLE II                                    __________________________________________________________________________    Effect of Blend Composition on Green Strength. Blends shown are for           Natsyn 200                                                                    with 5 and 10 phr of an 85/15 1-Butene/1-Hexene Copolymer.sup.1 in            BLACK-LOADED BANBURY STOCKS.                                                         5 PHR BLEND        10 PHR BLEND                                        Extended                                                                             Yield                                                                             Break          Yield                                                                             Break                                           Milling                                                                              Stress                                                                            Stress    Mooney                                                                             Stress                                                                            Stress    Mooney                                Time (Min.)                                                                          (psi)                                                                             (psi)                                                                             (% Elong)                                                                           (ML-4).sup.2                                                                       (psi)                                                                             (psi)                                                                             (% Elong)                                                                           (ML-4).sup.2                          __________________________________________________________________________    0      48  179 (1250)                                                                              77   57  270 (1050)                                                                              75                                    5      34  67  (1600)                                                                              59   45  62   (800)                                                                              53                                    10     32  45  (1500)                                                                              54   37  60  (1200)                                                                              49                                    20     29  26  (1950)                                                                              47   31  41  (1700)                                                                              44                                    __________________________________________________________________________     .sup.1 Molar charge composition; polymerization temperature: 30°       C., inherent viscosity, 2.9; melting temperature of 80° C.; and,       glass transition temperature of -35° C. (Differential thermal          analyzer).                                                                    .sup.2 Standard Mooney Viscosity Test, ASTM D 29772. Measurements at          212° F. using a large rotor.                                      

Table II shows addition of both 5 and 10 parts per hundred parts of theelastomer of the 85/15 butene/hexene copolymer resulted in improvedgreen strength as compared with Natsyn control valves in Table I.

                                      TABLE III                                   __________________________________________________________________________    Effect of Copolymer Composition on Green Strength of Blends with              Natsyn 200. Blends with 5 phr Copolymer, Black-Loaded Banbury                 __________________________________________________________________________    Stocks.                                                                       Polybutene.sup.1   95/5/1-Butene/1-Hexene.sup.2                               Milling                                                                           Yield                                                                             Break      Yield  Break                                               Time                                                                              Stress                                                                            Stress     Stress Stress                                              (min.)                                                                            (psi)                                                                             (psi)                                                                             (% Elong)                                                                            (psi)  (psi)  (% Elong)                                    __________________________________________________________________________    0   --  233   (500)                                                                              130    265      (660)                                      5   90  79  (1,200)                                                                              35     54     (1,400)                                      10  65  21  (1,200)                                                                              32     31     (1,940)                                      20  42  12  (1,900)                                                                              27     11     (2,040)                                      __________________________________________________________________________    90/10/1-Butene/1-Hexene.sup.3                                                                    85/15/1-Butene/1-Hexene.sup.4                              Milling                                                                           Yield                                                                             Break      Yield  Break                                               Time                                                                              Stress                                                                            Stress     Stress Stress                                              (min.)                                                                            (psi)                                                                             (psi)                                                                             (% Elong)                                                                            (psi)  (psi)  (% Elong)                                    __________________________________________________________________________    0   165 267   (460)                                                                              48     179    (1,250)                                      5   70  96    (630)                                                                              34     67     (1,600)                                      10  30  26  (2,500)                                                                              32     45     (1,500)                                      20  28  20  (2,000)                                                                              29     26     (1,950)                                      __________________________________________________________________________        ENDOTHERMIC PEAK, °C.                                                                 Inherent Viscosity, dl./g.                                 __________________________________________________________________________    .sup.1                                                                             72, 96, 118    --                                                        .sup.2                                                                             81, 104        5.1                                                       .sup.3                                                                             95 (estimated)                                                                               4.7                                                       .sup.4                                                                             80             2.9                                                       __________________________________________________________________________    80/20 1-Butene/1-Hexene.sup.5                                                                    70/30 1-Butene/1-Hexene.sup.6                              Milling                                                                           Yield                                                                             Break      Yield  Break                                               Time                                                                              Stress                                                                            Stress     Stress Stress                                              (min.)                                                                            (psi)                                                                             (psi)                                                                             (% Elong)                                                                            (psi)  (psi)  (% Elong)                                    __________________________________________________________________________    0   45  139 (1,200)                                                                              40     111      (950)                                      5   34  52  (1,700)                                                                              31     43     (1,120)                                      10  30  36  (1,750)                                                                              29     31     (1,580)                                      20  29  22  (2,070)                                                                              30     28     (1,610)                                      __________________________________________________________________________    90/10 1-Butene/1-Octene.sup.7                                                                    95/5/5 1-Butene/1-Octene/1,7-Octadiene.sup.8               Milling                                                                           Yield                                                                             Break      Yield  Break                                               Time                                                                              Stress                                                                            Stress     Stress Stress                                              (min.)                                                                            (psi)                                                                             (psi)                                                                             (% Elong)                                                                            (psi)  (psi)  (% Elong)                                    __________________________________________________________________________    0   43  154   (940)                                                                              65     147      (700)                                      5   32  49  (1,530)                                                                              32     43     (1,120)                                      10  29  34  (1,830)                                                                              31     34     (1,840)                                      20  26  14  (1,820)                                                                              29     20     (1,740)                                      __________________________________________________________________________        ENDOTHERMIC PEAK, °C.                                                                 INHERENT VISCOSITY, dl./g.                                 __________________________________________________________________________    .sup.5                                                                             53, 74         0.5 (number average molecular weight                      .sup.6                                                                            --              3.7     estimated to be 30,000)                           .sup.7                                                                             68             8.1                                                       .sup.8                                                                             64            --                                                         __________________________________________________________________________

                                      TABLE IV                                    __________________________________________________________________________    Blends of Natsyn 200 with 5 percent 1-Butene/1-Hexene (80/20)                 Copolymer.sup.1                                                               Compared with 5 percent 1-Butene/Propylene (80/20) Copolymer.sup.2            (Black-Loaded Banbury Stocks)                                                         1-Butene/1-Hexene Blend.sup.3                                                               1-Butene/Propylene Blend                                Milling Yield                                                                             Break     Yield                                                                             Break                                               Time    Stress                                                                            Stress    Stress                                                                            Stress                                              (min.)  (psi)                                                                             (psi)                                                                             (% Elong)                                                                           (psi)                                                                             (psi)                                                                             (% Elong)                                       __________________________________________________________________________    Natsyn                                                                        200 0   45  139 (1200)                                                                              80  155  (500)                                              5   34  52  (1700)                                                                              37  64  (1840)                                              10  30  36  (1750)                                                                              32  36  (1980)                                              20  29  22  (2070)                                                                              29  22  (2000)                                          __________________________________________________________________________     .sup.1 Molar charge ratio; inherent viscosity, 0.5.                           .sup.2 Molar charge ratio; polymerization temperature: 30° C.;         inherent viscosity, 4.7.                                                      .sup.3 Data on butene/hexene copolymer (5) from TABLE III shown here for      comparison with butene/propylene copolymer.                              

                                      TABLE V                                     __________________________________________________________________________    Effect of Addition of 5 percent 90/10 1-Butene/1-Hexene Copolymer.sup.1       On Green Strength of Cis-1,4-Polybutadiene and A Rubber Blend                 (Black-Loaded Banbury Stocks)                                                          CONTROL STOCKS                                                                              5% BUTENE/HEXENE BLENDS                                Milling  Yield                                                                             Break     Yield Break                                            Time     Stress                                                                            Stress    Stress                                                                              Stress                                           (min.)   (psi)                                                                             (psi)                                                                             (% Elong)                                                                           (psi) (psi) (% Elong)                                  __________________________________________________________________________    Budene.sup.2                                                                       0   19  7   (600) 68    45    (200)                                           5   17  3   (570) 24    11    (670)                                           10  18  5   (650) 27    11    (350)                                           20  19  5   (510) 24     9    (480)                                      Rubber                                                                        Blend.sup.3                                                                        0   37  60  (1810)                                                                              57    99    (790)                                           5   32  30  (1830)                                                                              37    39    (1490)                                          10  29  21  (1580)                                                                              40    31    (1370)                                          20  28  17  (1410)                                                                              37    26    (1120)                                     __________________________________________________________________________     .sup.1 molar charge ratio; inherent viscosity, 3.1.                           .sup.2 cis1,4-polybutadiene; commercially available from The Goodyear Tir     and Rubber Company.                                                           .sup.3 Blend containing 35/35/30 natural rubber (#1 ribbed smoked             sheet)/Budene/SBR (84% butadiene and 16% styrene extended with 37.5 parts     of oil).                                                                 

The data in Table III deomonstrates that the homopolymer of 1-butene, 5different copolymers of 1-butene and 1-hexene of varying compositionsand having significantly different melting temperatures and viscosities,a copolymer of 1-butene and 1-octene, and a terpolymer of 1-butene,1-hexene and 1,7-octadiene were effective in enhancing the greenstrength of Natsyn 200 when compared with the data in Table I for Natsyn200.

The data in Table IV shows that the 80/20 butene/propylene copolymer wasat least as effective as the 80/20 butene/hexene copolymer in enhancingthe green strength of Natsyn.

The blend of natural rubber, polybutadiene, and SBR with 5 percent of abutene/hexene copolymer, as set forth in Table V, gave improved greenstrengths over the control (without copolymer). Similar improvement ingreen strength was also observed for high cis-1,4-polybutadiene.

                                      TABLE VI                                    __________________________________________________________________________    Unvulcanized and Vulcanized Properties of Solution Blends.sup.1 of a          90/10 Butene/Hexene                                                           Copolymer with Natsyn 200.sup.2                                               __________________________________________________________________________    Natsyn 200 (parts/hundred rubber)                                                                  100     97      95                                       Butene/Hexene Copolymer (phr)                                                                      0       3       5                                        __________________________________________________________________________     UNVULCANIZED PROPERTIES                                                      __________________________________________________________________________    Green Tensile Strength (psi)                                                                       21      44      178                                      Elongation at Break (%)                                                                            1650    500     500                                      Compound Mooney (MS-11/2).sup.3                                                                    43      48      51                                       Raw Polymer Stability:                                                        (Mooney ML-4)                                                                  0 days              87      75      75                                       21 days              70      64      62                                       % decrease             19.5    14.7    17.3                                   __________________________________________________________________________     .sup.1 Hexane cements of Natsyn 200 and the copolymer were blended in         solution by stirring, dried and finished by steam stripping the solvent       (hexane) and dewatering the resultant crumb rubber blend.                     .sup.2 Natsyn 200 is commercially available from The Goodyear Tire and        Rubber Company.                                                               .sup.3 Standard Mooney tests found in ASTM D29772. Measurements at            212° F. using a small rotor.                                      

     VULCANIZATE PROPERTIES.sup.4                                                 __________________________________________________________________________    AT 77° F.                                                               300% Modulus (psi)  812     928     928                                       Tensile Strength (psi)                                                                            4263    4147    4002                                      Elongation at Break (%)                                                                           680     680     690                                      AT 200° F.                                                              Tensile Strength (psi)                                                                            2880    2920    3120                                      Elongation at Break (%)                                                                           680     630     670                                      __________________________________________________________________________     .sup.4 Stocks were compounded according to the following recipe and cured     at 275° F. for?  40 minutes:?                                     

                      pm                                                                     Rubber  100                                                                   HAF black                                                                            35                                                                     Zinc Oxide                                                                           3.0                                                                    Stearic Acid                                                                         2.0                                                                    Antioxidant                                                                          1.0                                                                    Sulfur 2.0                                                                    Accelerator                                                                          0.8                                                                    TOTAL  143.8                                                       __________________________________________________________________________

Table VI shows the results of solution blending hexane cements of thecopolymer with Natsyn 200. Green Strength is improved with both 3 and 5percent additions of copolymer and the vulcanizate properties areessentially unchanged.

Blends containing reclaim rubber were made and tested. The analysis ofthe reclaim rubber used as the elastomer was as follows:

    ______________________________________                                        Natural rubber        30 percent                                              SBR                   35 percent                                              Polybutadiene         35 percent                                              Acetone extractables  25 percent                                              Total Sulfur          1.5 percent                                             Free carbon           22 percent                                              Ash                   12 percent                                              ______________________________________                                    

The recipe and blending conditions of the reclaimd rubber were asfollows:

    ______________________________________                                        MATERIAL    PHR     BLENDING CONDITIONS                                       ______________________________________                                        Reclaim     200     Brabender mixed,                                          Copolymer.sup.1                                                                           50      51/2 minutes @ 50 RPM                                     zinc oxide  5       225° F. oil circulating                            stearic acid                                                                              2       reservoir temperature                                     ______________________________________                                         .sup.1 95:5 butene/hexene copolymer (See TABLE III).                     

The reclaim rubber-butene copolymer blend was then tested and the datais shown in Table VII.

                  TABLE VII                                                       ______________________________________                                                   YIELD   BREAK                                                                   STRESS    (STRESS)                                               COMPOSITION  (psi)     (psi)     (% Elongation)                               ______________________________________                                        Reclaim control                                                               (without copolymer)                                                                        45        45        (240)                                        Reclaim rubber/co-                                                            polymer blend                                                                              97        97        (190)                                        ______________________________________                                    

Thus, as is readily apparent from TABLE VII, the addition of abutene/hexene copolymer of reclaim rubber improved its yield stress andstress-at-break by at least 100 percent.

As is apparent to those skilled in the art, many modifications of theinvention can be made without departing from the spirit of the inventiondisclosed and described herein. The scope of this ivention is measuredby the appended claims.

What is claimed is:
 1. A prevulcanization process for producingelastomer blends, comprising, improving the prevulcanization greenstrength of an elastomer blend bymixing a semi-crystalline butenepolymer having a number average molecular weight of from about 30,000 toabout 500,00 with an elastomer to produce said elastomer blend, theamount of said butene polymer ranging from about 2 parts to about 25parts per 100 parts of said elastomer, said butene polymer selected fromthe class consisting of polybutene and interpolymers made from 1-butenemonomer and at least one monomer selected from the class consisting ofalpha-olefins having 2 through 16 carbon atoms and nonconjugated dieneshaving the general formula: ##STR8## where R₁, R₂, and R₃ is a hydrogen,a lower alkyl group containing from 1 to 4 carbon atoms, or an arylgroup; where R₄ is an aryl group or a lower alkyl group containing from1 to 9 carbon atoms, and n is an integer having a value of from 1 to 6,and wherein the said R₁ 's in the ##STR9## group may be similar todissimilar; and non-conjugated alpha, omega-polyenes having from 6 to 36carbon atoms which may or may not contain internal unsaturation, whereinbutene in said interpolymers comprises from 99.9 to 65 mole percent ofthe total monomers, said elastomer selected from the class consisting ofnatural cis-1,4-polyisoprene and elastomers made from monomers selectedfrom the class consisting of conjugated dienes having from 4 to 10carbon atoms, interpolymers of said dienes among themselves or withmonomers selected from the class consisting of vinyl substitutedaromatic hydrocarbon compounds having from 8 to 12 carbon atoms, andpolyalkenylenes.
 2. A process according to claim 1, wherein the meltingtemperature of said butene polymer ranges from about 55° C. to about125° C. and wherein the inherent viscosity of said butene polymer isfrom about 0.5 dl/g to about 10.0 dl/g.
 3. A process according to claim2, wherein said butene polymers are selected from the class consistingof polybutene, a copolymer of 1-butene and ethylene, a copolymer of1-butene and propylene, a copolymer of 1-butene and 1-hexene, acopolymer of 1-butene and 1-octene, a terpolymer of 1-butene, 1-octeneand 1,7-octadiene, and a terpolymer of 1-butene, 1-hexane and 1-octene.4. A process according to claim 3, wherein said elastomer is selectedfrom the class consisting of natural cis-1,4-polyisoprene, syntheticcis-1,4-polyisoprene, cis-1,4-polybutadiene, a copolymer of styrene andbutadiene, and a copolymer of cyclopentene and dicyclopentadiene.
 5. Aprocess according to claim 4, wherein the amount of butene in saidbutene interpolymer ranges from about 95 to about 70 mole percent of thetotal monomers, wherein the amount of said butene polymer ranges fromabout 3 parts to about 12 parts per 100 parts of said elastomer, andwherein said inherent viscosity of said butene polymer ranges from about1.0 to about 4.0 dl/g, and wherein the molecular weight of saidelastomer ranges from about 50,000 to about 300,000.
 6. A composition,comprising;a blend of a semi-crystalline butene polymer having a numberaverage molecular weight of 30,000 to about 500,000 with an elastomer,said blend having improved green strength, the amount of said butenepolymer ranging from about 2 parts to about 25 parts per 100 parts ofsaid elastomer, said butene polymer selected from the class consistingof polybutene and interpolymers made from 1-butene monomer and at leastone monomer selected from the class consisting of alpha-olefins having 2through 16 carbon atoms and non-conjugated dienes having the formula:##STR10## where R₁, R₂, and R₃ is a hydrogen, a lower alkyl groupcontaining from 1 to 4 carbon atoms, or an aryl group; where R₄ may bean aryl group or a lower alkyl group containing from 1 to 9 carbonatoms, and n is an integer having a value of from 1 to 6, and whereinthe said R₁ 's in the ##STR11## group may be similar or dissimilar; andnon-conjugated alpha, omega-polyenes having from 6 to 36 carbon atomswhich may or may not contain internal unsaturation, wherein butene insaid interpolymers comprises from 99.9 to 65 mole percent of the totalmonomers, said elastomer selected from the class consisting of naturalcis-1,4-polyisoprene and elastomers made from monomers selected from theclass consisting of conjugated dienes having from 4 to 10 carbon atoms,interpolymers of said dienes among themselves or with monomers selectedfrom the class consisting of vinyl substituted aromatic hydrocarboncompounds having from 8 to 12 carbon atoms, and polyalkylenes.
 7. Anelastomer blend composition according to claim 6, wherein the meltingtemperature of said butene polymer ranges from about 55° C. to about125° C. and wherein the inherent viscosity of said butene polymer isfrom about 0.5 dl/g to about 10.0 dl/g.
 8. An elastomer blendcomposition according to claim 7, wherein said butene polymers areselected from the class consisting of polybutene, a copolymer of1-butene and ethylene, a copolymer of 1-butene and propylene, acopolymer of 1-butene and 1-hexene, a copolymer of 1-butene and1-octene, a terpolymer of 1-butene, and 1-octene and 1,7-octadiene, anda terpolymer of 1-butene, 1-hexene and 1-octene.
 9. An elastomer blendcomposition according to claim 8, wherein said elastomer is selectedfrom the class consisting of natural cis-1,4-polyisoprene, syntheticcis-1,4-polyisoprene, cis-1,4-polybutadiene, a copolymer of styrene andbutadiene and a copolymer of cyclopentene and dicyclopentadiene.
 10. Anelastomer blend composition according to claim 9, wherein the amount ofbutene in said butene interpolymers ranges from about 95 to about 70mole percent of the total monomers, wherein the amount of said butenepolymer ranges from about 3 parts to about 12 parts per 100 parts ofsaid elastomer, and wherein said inherent viscosity of said butenepolymer ranges from about 1.0 to about 4.0 dl/g, and wherein themolecular weight of said elastomer ranges from about 50,000 to about300,000.